1. Field of the Invention
The present invention generally relates to a rotary electric machine. More specifically, the present invention relates to a stator structure for a rotary electric machine having medium cooling passages.
2. Background Information
An example of a rotary electric machine or motor is disclosed in Japanese Laid-Open Patent Publication No. 4-364343. In this publication, the rotary electric machine has a stator with the stator slots (grooves that house the coils) being used as cooling medium passages so that the stator coils and the stator can be cooled directly in order to cool the rotary electric machine efficiently.
In the rotary electric machine of Japanese Laid-Open Patent Publication No. 4-364343, molds are arranged adjacent an inner peripheral surface of the stator and located within the axial slots of the stator core, and then an engineering plastic material is injected to fill the space defined by the stator core and the molds. Once the plastic material has hardened, the slot openings in the stator core are blocked by the plastic material so that axial cooling medium passages are formed in the stator core.
In view of the above, there exists a need for an improved stator structure having cooling passages for use with a rotary electric machine. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.
It has been discovered that in order to mold a resin material on the inside surface of a stator core, a mold having a slightly smaller diameter than the inside surface of the stator core is arranged inside the stator core, and then an annular space between the mold and the stator core is filled with the resin material. However, it is difficult to manage the process to make the thickness of the resin material uniform around the inner circumference of the stator core. Also it is difficult to form a thin resin film that does not interfere with a rotor that rotates inside the stator core. Also, if the adhesion between the stator core and the resin material is poor, then the liquid sealing performance of the cooling medium passages in the stator core will degrade and the cooling medium may leak out.
Thus, one object of the present invention is to provide a stator structure for use with a rotary electric machine that solves the above-noted problems.
In accordance with one aspect of the present invention, a stator structure for a rotary electric machine basically comprises an annular stator core, a plurality of protrusions, and an annular resin layer. The annular stator core includes a plurality of axially extending slots and an inner peripheral surface defining a rotor receiving opening with a center axis. The protrusions extend from the inner peripheral surface of the stator core. The protrusions have a predetermined radial thickness. The annular resin layer is formed on the inner peripheral surface of the stator core. The annular resin layer has a radial thickness along inner peripheral surface of the stator core that is substantially equal to the radial thickness of the protrusions.
These and other objects, features, aspects and advantages of the present invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses a preferred embodiment of the present invention.